1. Field of the Invention
The present invention relates to a method and to a burner for burning of oxygen, and more particularly for use with heating furnaces.
2. Description of the Related Art
Normally, when hydrocarbons are burned in combination with oxidants having a high oxygen content, flame temperatures within the furnace exceed 2000° C. and furnace atmospheres with very high partial pressures of carbon dioxide and water vapor are present. That condition also gives rise to drawbacks, such as high NOx content and problems of local overheating.
There is a strong desire to provide burners that have emission-lowering properties.
In Swedish patent application number 0402223-2, a method is disclosed for burning a fuel with an oxidant in a heating furnace, wherein the fuel and the oxidant are supplied to a burner head. According to that application, in a first step fuel and oxidant are discharged from the burner head close to each other, so that the combustion essentially takes place close to and up to a certain distance from the burner head. Combustion proceeds until a temperature exceeding the auto ignition temperature of the fuel is reached inside the furnace, after which the fuel and the oxidant, in a second step, are instead discharged from the burner head at a distance from each other. Consequently, the combustion essentially takes place at a distance from the burner head at least as large as the diameter of the burner head, and outwardly from the burner.
According to that application, the intent is to lower the oxygen content in the combustion zone through separation, high pressure, and optimized positioning of the nozzles, even though the oxidant has an oxygen content of more than 80%. That is accomplished by the use of a nozzle configuration that gives rise to a large underpressure over those surfaces of the nozzle that do not have nozzles for the medium. Because of the underpressure, flue gases are sucked in from the furnace atmosphere and are rapidly and turbulently mixed with the out-flowing media. The mixture medium, i.e., the furnace atmosphere, typically has an oxygen content of 0.5-10%. The remaining gas is CO2, H2O, and N2 in various amounts.
Since the CO2, H2O, and N2 do not actively take part in the combustion, those compounds act as a “combustion brake.” The dilution of the oxygen and the fuel is very extensive, and oxygen rates during the combustion typically reach 7-15%, despite the use of pure oxygen gas.
The present invention is directed to overcoming those problems.